Field of the Invention
The invention relates to a valve for controlling a purging fluid for marine speedometer lines.
Marine speedometers designed for use in pleasure craft are usually pitot pressure-type instruments. These speedometers are connected by a tube to a sender unit below the waterline of the boat. These sender units are known as impact tubes. The pressure of the water entering the impact tube is transmitted to the speedometer through the flexible tube. Such a marine speedometer is essentially a pressure guage for measuring the pressure of the water which is proportional to the speed of the boat.
It is very common for such speedometers to be rendered inoperative due to vegetation or other debris entering the opening in the impact tube. Once the tube is clogged, the pressure is no longer transmitted to the speedometer. Removing this debris is awkward and usually cannot be accomplished until the boat returns to shore.
Marine speedometers and the like are shown in such earlier U.S. Pat. No. 2,362,298 to Newell, U.S. Pat. No. 3,050,996 to Henderson, U.S. Pat. No. 3,327,530 to Lepird and U.S. Pat. No. 3,349,615 to Finkl.
A similar problem with fouling has been encountered in the pitot tubes of aircraft. U.S. Pat. No. 4,174,049 to Bolen discloses an apparatus for purging pitot tubes of aircraft. The apparatus includes a disposable, replacable cylinder of compressed gas and a valve. The valve disconnects instruments from the regular pitot tube when the lines are being purged. Another device for purging pitot tubes is disclosed in U.S. Pat. No. 3,380,298 to Hanson. Both of these patents show devices which are far too complex and expensive for practical application in pleasure boats.